U.S. patent number 4,288,690 [Application Number 06/088,963] was granted by the patent office on 1981-09-08 for illumination system.
This patent grant is currently assigned to Recognition Equipment Incorporated. Invention is credited to Medford D. Sanner.
United States Patent |
4,288,690 |
Sanner |
September 8, 1981 |
Illumination system
Abstract
A system for uniformly illuminating a field of information is
provided for optical character readers having a scanning device
loosely constrained in movement. Lamps are symmetrically located
about the optical axis of a sensor and enclosed within an
illuminator. The sides of the illuminator converge at one end to
port having dimensions defined by the field to be viewed. A plate
between the lamps and the sensor partially encloses the second end
of the illuminator with an aperture therein symmetrical to the
optical axis of the sensor. The sides of two opposite walls of the
illuminator adjacent to the port are cut out to remove a portion
thereof to eliminate internal reflections and to give the operator
a better view of the information to be scanned.
Inventors: |
Sanner; Medford D. (Irving,
TX) |
Assignee: |
Recognition Equipment
Incorporated (Irving, TX)
|
Family
ID: |
22214536 |
Appl.
No.: |
06/088,963 |
Filed: |
October 29, 1979 |
Current U.S.
Class: |
250/216;
250/568 |
Current CPC
Class: |
G06K
9/2009 (20130101); G06K 7/10881 (20130101) |
Current International
Class: |
G06K
9/20 (20060101); G06K 7/10 (20060101); H01J
003/14 () |
Field of
Search: |
;235/472,473,455
;250/227,566,567,568,569,570,239,216 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Nelms; David C.
Attorney, Agent or Firm: Vandigriff; John E.
Claims
I claim:
1. Improvement in a data field illuminator for uniformly
brightening a data field viewed by a photo sensor array in an
optical character recognition system wherein the illuminator has
side walls converging from an enclosure plate to a first aperture,
the improvement comprising two additional apertures in opposite
side walls of said illuminator, said apertures adjacent to said
first apertures.
2. The illuminator according to claim 1 wherein said additional
apertures are generally rectangular.
3. An illuminator for uniformly brightening a data field viewed by
a photo sensor array comprising enclosure walls symmetrical to the
optical axis of said array and joined so as to form a first
aperture remote from said array and diverging to an end
intermediate to said array and said first aperture and having a
second aperture aligned with said first aperture, third and fourth
apertures in said enclosure walls adjacent said first aperture, and
at least one source of illumination adjacent said second
aperture.
4. The system according to claim 3 wherein said third and fourth
apertures are spaced opposite each other in said enclosure walls.
Description
Various problems described above have been avoided through the
invention defined in U.S. Pat. No. 4,005,286 which uses an
illumination system enclosed in a converging illuminator and having
portions of the wall coated with a high defuse reflective material
while other parts are coated with a low defuse reflectance
material. The coating serves the purpose intended but increases the
cost of the illuminator system through the extra step of having to
apply the coatings.
The present invention provides a system wherein the application of
the coatings is not necessary and other problems in prior art
systems are reduced and/or eliminated.
SUMMARY OF THE INVENTION
An illumination system is provided for hand held and other types
scanning devices used with optical character recognition systems
and operated in a loosely constrained environment. An illuminator
enclosure employs a light source symmetrical to the optical axis of
a sensor. Walls of the illuminator converge to define a port to be
passed in registration with the data field. Opposite walls of the
illuminator adjacent to the port have portions removed therein to
prevent internal reflection by those portions of the walls which
are cut out and also to provide a better field of view for the
person using the scanner. The improved field of view aids in moving
the scanner over the data to be read and yields more accurate
registration therewith.
A plate located between the light source and the sensor partially
closes the end opposite the port with an aperture in the plate
symmetrical to the optical axis of the sensor preferably tapered to
direct primary light away from the sensor.
FIELD OF THE INVENTION
This invention relates generally to a system for uniform
illumination of data fields passing in registration with the
optical character recognition systems and specifically to an
illuminating system embodied within the hand held scanning device
wherein portions of two walls of the illuminator are moved to
prevent internal reflection and to provide a better view of the
material being scanned.
DESCRIPTION OF THE PRIOR ART
Systems for automatically reading alphanumeric data fields have
been developed for various uses. In some systems registration
between the scanning system and a document may be controlled to
minimize reading problems. In merchandisizing operations, however,
a hand held reader is used to scan data fields on merchandise or
tags. Because of variations in the relative movement between the
scan unit and the data field misregistrations occur which cause
corresponding errors in character identification. Further cause of
such reading errors is the nonuniform illumination resulting from
data field skew, tilt and depth of field variations relative to the
scanning device.
To alleviate such illumination problems the conventional approach
has been to alter the optical design, enclose the optical system
with a reflector case, or increase the light intensity and number
of lamps within the scan head. Such alternative designs results in
complex and bulky optical systems, heating of the scan head,
subsequent discomfort to user, and increased power consumption.
Where mirror-type reflectors have been used, the illumination
problem has been aggravated by the occurence of hot spots and
shadows in the data field caused by deformities in the reflector
surface.
DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention and the
technical advance represented thereby reference is now made to the
following description taken in conjunction with accompanying
drawings in which:
FIG. 1 is a side view of a hand held scanning device employing the
invention and having an outer cover cut away to expose internal
component parts;
FIG. 2 is a perspective view of an illuminator in accordance with
the invention in use in the system of FIG. 1;
FIG. 3 is a sectional view of the illuminator with lamps seated in
place;
FIG. 4 is a sectional view of the illuminator looking toward
another side thereof; and
FIG. 5 is another embodiment of an illuminator having an oval cross
section .
DESCRIPTION OF PREFERRED EMBODIMENT
A hand-held scan head or reader 10, as illustrated in FIG. 1,
includes an outer housing 11 and a detachable illuminator 12.
Housing 11 provides chambers for a video processing unit 13 in
electrical communication with external data processing and
character recognition units by way of cable 14. A two-dimensional
photosensor array 16 in housing 11 is repeatedly and automatically
scanned by unit 13 through conductors 15a. A lens system 17 is
positioned ahead of array 16. Lens system 17 gathers light
reflected by a data field through illuminator 12 and focuses such
light upon the surface of the sensor array 16. Lamps 18 and 19 are
energized by conductors 15b of cable 14 and are seated within
apertures formed in the upper end of illuminator 12. The filaments
of the lamps extend into the interior of the illuminator.
In merchandising operations, wand 10 is passed in registration with
a data field or merchandise tag 20. The light generated by lamps 18
and 19 is dispersed by the reflecting inner walls of illuminator 12
so as to illuminate tag 20. Light reflected by the data field 20
then passes through port 12a and an aperture 12b of illuminator 12,
and is gathered by lens system 17 and focused upon sensor array
16.
It will be recognized that the sweep of reader 10 across the data
field 20 may not be at a uniform velocity and may follow a
nonlinear path which is not parallel with the plane of the tag.
Further, the port 12a may be skewed during all of part of its
travel across the data field. The distance 12h may vary from zero
but preferably will remain close to zero. The necessarily loose
constraints upon use causes undesirable errors in data recognition
which are further compounded by variances in illumination over the
field of view.
The present invention provides an illuminator which redirects the
light produced from sources within wand 10 so as to provide not
only uniform two-dimensional illumination to accomodate large
tolerance in skew, and tilt, but also to accomodate large
tolerances in depth of field (DOF) as the operator varies the
distance 12h between a merchanidsing tag and the wand port 12a.
Such depth of field variations may occur simply because data field
may be placed on irregularly shaped merchandise.
As better seen in FIGS. 2 and 3, illuminator 12 is a four-sided
enclosure having side walls 12f and 12g which converge to a port
12a at one end, and diverge to a larger closure plate 12e in the
opposite end. A central rectangular aperture 12b is formed in plate
12e. Circular apertures 12c and 12d are symmetrically placed at the
ends of aperture 12b. It is to be understood that while aperture
12b is shown as rectangular in FIGS. 2 and 3, other configurations
including a circular shape also may be used.
The walls of plate 12e defining aperture 12b are tapered to diverge
into illuminator 12 at an angle relative to the filaments in bulbs
18 and 19 to reflect light from lamps 18 and 19 back into the
interior of the illuminator. Primary light is prevented thereby
from interfering with the two-dimensional image reflected by a data
field through aperture 12b.
In the form illustrated in FIG. 3, lamps 18 and 19 are seated
within an aperture 12d and 12c, respectively, with filaments 18a
and 19a positioned within the interior of the illuminator chamber.
Emanating from the lamp 18 are rays of light, 18b and 18c, which
strike an interior wall side 12f below a point over midway down the
side wall towards the port 12a and are reflected toward port 12a.
When the illuminator 12 is displaced a distance 12h (see FIG. 1)
from data field 20, the rays converge to form highly illuminated
area 20a on the data field. In addition, the law of inverse square
operates upon the reflected rays to cause a rapid fall-off in
illumination at the edges of port 12a as the distance between the
port and the data field 20 increases.
To prevent these internal reflections from highly illuminated
points within the illuminator, portions of the illuminator walls
are removed to provide the opening 12k. The eliminating of the
reflecting inner walls eliminate hot spots in the data field to be
viewed. The cut away portions of the wall permit light to emerge
from the illuminator onto the data field and permit the operator to
view the data directly under the illuminator to help reduce skew,
and tilt which may occur if the scanner is not held squarely
adjacent to the data field. The elimination of the coated interiors
of the illuminator and the removed portions decreases the material
required to manufacture the illuminator thereby reducing the cost
thereof. It has been found that the illuminator in the present
invention, while having a lower cost, adequately illuminates the
data field without causing hot spots or undue internal reflections
and provides a better view of the data view thereby permitting the
operator to more accurately scan the data field.
Another embodiment of the illuminator is illustrated in FIG. 5. The
illuminator shown has an oval cross section. Actually, any
geometrical cross section is suitable as long as unwanted
reflections and/or hot spots are not caused by the side walls.
In accordance with the invention there is provided an optical
character reader illuminator which disperses light emanating from a
light source so that it uniformly illuminates the data field being
scanned and provides the advantages enumerated above.
Having described the invention in connection with certain specific
embodiments, it is to be understood that further modifications will
be apparent to those skilled in the art and it is intended to cover
such modifications as fall within the scope of the apended
claims.
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